1090329 - reftest 1082844-1 fails on Android and B2G-emulator due to misplaced content in vertical-rl block

Status: RESOLVED FIXED

(Core :: Layout: Block and Inline, defect)

Description

[Jonathan Kew [:jfkthame]]

According to https://treeherder.mozilla.org/ui/#/jobs?repo=try&revision=e6519895b781, it looks like this reftest is going to go orange when we enable vertical support. :(

Checking the reftest-analyzer view, this looks like a real bug, where the content of the test <div> is misplaced upwards and slightly right in the testcase, while the reference renders correctly. So this needs debugging and fixing before we can ship vertical support on mobile.

Offhand, I'm not sure why this should affect mobile, while working correctly on desktop platforms.

Comment 1

[Jonathan Kew [:jfkthame]]

This appears to be triggered by incorrect (vertical) glyph advances when using the freetype backend (which also affects the GDI backend, actually, and results in terribly-spaced text). The platform-specific GetGlyphWidth method is returns the horizontal glyph width, which should never be used by GetGlyphVAdvance. (I think this code is a remnant of an early version of the vertical-text support, where I was going to instantiate separate gfxFont instances for vertical vs horizontal use.)

Comment 2

[Jonathan Kew [:jfkthame]]

Attachment: gfxHarfBuzzShaper::GetGlyphVAdvance should never use the backend-specific GetGlyphWidth method, which is for horizontal width only

With this removed, the 1082844-1 test no longer fails on mobile platforms.

Comment 3

[Simon Montagu :smontagu]

Comment on attachment 8541846 [details] [diff] [review]
gfxHarfBuzzShaper::GetGlyphVAdvance should never use the backend-specific GetGlyphWidth method, which is for horizontal width only

Review of attachment 8541846 [details] [diff] [review]:
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Sounds reasonable, though I'm not exactly familiar with this code.

Comment 4

[Jonathan Kew [:jfkthame]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/67960aabce3a

Comment 5

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/67960aabce3a